This invention relates to a novel resinous polymer and to a solderable or tinnable magnet wire and methods for making the same. More particularly, the invention relates to a class of polymers which have a plurality of amide, imide and ester groups therein which are cross linked utilizing a polyfunctional polycarboxylic acid. Additionally, and more particularly, the invention relates to a tinnable or solderable magnet wire insulated with the novel polymer of the invention which has all of the physical, mechanical, chemical and electrical properties of good magnet wire insulation material while at the same time having the capability of being removed from the electrical conductor of the magnet wire by immersing the magnet wire in a solder bath heated to elevated temperatures.
Magnet wires which are tinnable and solderable are well known. In this application the terms "tinnable" and "solderable" are used synonymously. Both expressions "tinnable" and "solderable" means that when a "tinnable" and "solderable" magnet wire is immersed in a solder bath heated to an elevated temperature, the insulation of the magnet wire is readily destroyed and detached from the conductor of the magnet wire over that portion of the conductor that has been immersed in the bath so that bare wire is exposed and can be directly used for making electrically conductive connections as by soldering. To this end, the magnet wire insulation should be removed as quickly as possible, i.e. in a matter of seconds, following its immersion in the solder bath. The shorter the contact time, the easier it is to remove the insulation and hence to obtain a commercially advantageous procedure. Baths of tin or tin alloys are normally used as the solder bath for this purpose thus the synonymous use of the words "tinnable" and "solderable". Deinsulation and soldering are carried out in basically the same way in the production of printed circuits and the like.
Prior solderable insulating coatings have been produced on electrical conductors like coating conductors with solutions containing compounds with at least two hydroxyl groups, a portion of which is at least trifunctional or more highly functional and masked by higher functionalized isocyanates. The disadvantage of these known coatings is that they show very little resistence to heat and chemicals; and thus, do not possess the thermal properties desired in many magnet wire applications. Therefore, it would be highly desirable to provide an improved tinnable and solderable magnet wire having an improved thermal stability, while still being "tinnable" and possessing all of the good physical, mechanical, chemical and electrical properties of magnet wire.
On the other hand, essentially linear polyester polymer materials and an essentially linear amide-imide materials have long been available and used as magnet wire insulation materials. Both thermoplastic and thermosettable essentially linear polyester resin materials have been heretofore proposed. See for example: British Pat. No. 978,717 British Pat. No. 1,115,919 Canadian Pat. No. 706,940 Canadian Pat. No. 781,993 French Pat. No. 1,416,443 U.S. Pat. No. 3,293,248 U.S. Pat. No. 3,297,785 U.S. Pat. No. 3,312,573 U.S. Pat. No. 3,342,780 U.S. Pat. No. 3,382,203 U.S. Pat. No. 2,268,586 U.S. Pat. No. 2,333,639 U.S. Pat. No. 2,686,739 U.S. Pat. No. 2,691,006 U.S. Pat. No. 2,889,304 U.S. Pat. No. 2,936,296 U.S. Pat. No. 3,022,200 U.S. Pat. No. 3,141,859 U.S. Pat. No. 3,179,634 U.S. Pat. No. 3,201,276 U.S. Pat. No. 3,211,585 U.S. Pat. No. 3,240,626 U.S. Pat. No. 3,249,578 U.S. Pat. No. 3,390,131 U.S. Pat. No. 3,428,426 U.S. Pat. No. 3,445,477 U.S. Pat. No. 3,446,758 U.S. Pat. No. 3,448,089 U.S. Pat. No. 3,480,589 U.S. Pat. No. 3,489,696 U.S. Pat. No. 3,518,219 U.S. Pat. No. 3,518,230 U.S. Pat. No. 3,553,215 U.S. Pat. No. 3,576,774 U.S. Pat. No. 3,578,639 U.S. Pat. No. 3,699,082 U.S. Pat. No. 3,790,530
Numerous polyamide polymers, polyamide-imide polymers and polyimide polymers have also been proposed. These polymers generally have better thermal properties than the polyester polymers, but are appreciably more expensive than the polyester polymers. Thus, while these polymers also have been used as magnet wire enamels, their use has been limited to applications which can tolerate the increased cost thereof. Such polymers have also been disclosed; see for example: British Pat. No. 570,858 British Pat. No. 627,205 British Pat. No. 810,489 British Pat. No. 1,009,956 British Pat. No. 1,060,159 British Pat. No. 1,155,230 British Pat. No. 1,160,097 British Pat. No. 1,168,978 U.S. Pat. No. 3,347,828 U.S. Pat. No. 3,445,477 U.S. Pat. No. 3,451,848 U.S. Pat. No. 3,471,444 U.S. Pat. No. 3,472,815 U.S. Pat. No. 3,475,212 U.S. Pat. No. 3,485,796 U.S. Pat. No. 3,489,696 British Pat. No. 1,171,242 British Pat. No. 1,175,555 British Pat. No. 1,217,041 British Pat. No. 1,220,590 British Pat. No. 1,234,252 Canadian Pat. No. 701,460 French Pat. No. 1,473,600 U.S. Pat. No. 2,268,586 U.S. Pat. No. 2,621,168 U.S. Pat. No. 3,179,635 U.S. Pat. No. 3,179,639 U.S. Pat. No. 3,260,691 U.S. Pat. No. 3,300,420 U.S. Pat. No. 3,314,923 U.S. Pat. No. 3,493,540 U.S. Pat. No. 3,509,106 U.S. Pat. No. 3,518,219 U.S. Pat. No. 3,518,230 U.S. Pat. No. 3,539,537 U.S. Pat. No. 3,541,038 U.S. Pat. No. 3,546,152 U.S. Pat. No. 3,547,895 U.S. Pat. No. 3,553,159 U.S. Pat. No. 3,554,984 U.S. Pat. No. 3,562,217 U.S. Pat. No. 3,575,891 U.S. Pat. No. 3,578,639 U.S. Pat. No. 3,592,789 U.S. Pat. No. 3,696,077 U.S. Pat. No. 3,790,530
The demand for new polymers for use as magnet wire insulation materials which have higher and more reliable thermal life, while at the same time, are less expensive to manufacture and to apply than the polyamide, polyamide-imide, and polyimide polymers continues. To meet this demand, there had been proposed several modified polyamide, polyimide and polyester polymer materials. For the most part, these materials are polyamide ester resin materials, polyimide ester resin materials or polyamide-imide-ester resin materials. See for example: British Pat. No. 1,242,715 Canadian Pat. No. 771,126 U.S. Pat. No. 2,547,113 U.S. Pat. No. 2,626,223 U.S. Pat. No. 3,425,866 U.S. Pat. No. 3,426,098 U.S. Pat. No. 3,428,486 U.S. Pat. No. 3,458,480 U.S. Pat. No. 2,777,830 U.S. Pat. No. 2,821,517 U.S. Pat. No. 3,136,738 U.S. Pat. No. 3,255,069 U.S. Pat. No. 3,338,743 U.S. Pat. No. 3,354,126 U.S. Pat. No. 3,361,593 U.S. Pat. No. 3,390,118 U.S. Pat. No. 3,493,544 U.S. Pat. No. 3,505,272 U.S. Pat. No. 3,551,383 U.S. Pat. No. 3,555,113 U.S. Pat. No. 3,578,638 U.S. Pat. No. 3,699,082 U.S. Pat. No. 3,793,250 U.S. Pat. No. 3,917,892 U.S. Pat. No. 3,922,465 U.S. Pat. No. 3,732,168 U.S. Pat. No. 3,869,428 U.S. Pat. No. 4,141,886
In general, some such materials are thermoplastic, some are thermosettable materials, some are crosslinked thermoplastic materials and some are crosslinked thermosettable materials. For the most part all such materials contain both aliphatic and aromatic groups. In general, the linear polymers have more flexibility than the nonlinear, crosslinked materials, and the totally aromatic polymers have a higher and more reliable thermal life, but are more expensive than the totally aliphatic polymers. Thus, each of the above-identified modified polyamide, polyester, and polyimide polymers represent compromises in thermal life, cost, flexibility, and other physical, mechanical, chemical and electrical properties.
However, the magnet wire industry in general thought that these polyester, polyamide, polyamide-imide, and polyimide polymers could not be used as tinnable and solderable magnet wire insulation materials, because it was not expected that these coatings would be capable of being destroyed quickly enough in a solder bath to make it possible to obtain any commercial useful degree of solderability or tinnability within the parameters discussed hereinabove. In fact, each of the above-identified magnet wire insulation materials applied to conductors by conventional techniques to form magnet wire do not produce a useful tinnable or solderable magnet wire.
The afore-mentioned linear polyester polymers and polyamide, polyamide-imide and polyimide polymers all have suitable physical, mechanical, chemical and electrical properties to be good magnet wire insulation material. However, none of those materials have heretofore been utilized to produce solderable and tinnable magnet wire insulation coating materials. None of these materials have the opposing properties of both the physical, mechanical, chemical and electrical properties of good magnet wire insulation on the one hand, while on the other hand, high thermolability in a solder bath. Because of their good magnet wire insulation properties, however, it would be highly desirable to utilize the afore-mentioned polyester, polyamide, polyamide-imide, polyimide polymers as tinnable or solderable magnet wire insulation materials if the thermal ability in a solder bath be devised.